Greater Sage-Grouse nest bowls buffer microclimate in a post-megafire landscape although effects on nest survival are marginal

Abstract

Temperature at fine spatial scales is an important driver of nest site selection for many avian species during the breeding season and can influence nest success. Sagebrush (Artemisia spp.) communities have areas with high levels of vegetation heterogeneity and high thermal variation; however, fire removes vegetation that provides protection from predators and extreme environmental conditions. To examine the influence of microclimates on Greater Sage-Grouse (Centrocercus urophasianus) nest site selection and nest success in a fire-affected landscape, we measured black bulb temperature (Tbb) and vegetation attributes (e.g., visual obstruction) at 3 spatial scales (i.e. nest bowl, microsite, and landscape) in unburned and burned areas. Nest bowls exhibited greater buffering of Tbb than both nearby microsites and the broader landscape. Notably, nest bowls were warmer in cold temperatures, and cooler in hot temperatures, than nearby microsites and the broader landscape, regardless of burn stage. Nest survival (NS) was higher for nests in unburned areas compared to nests in burned areas (unburned NS = 0.43, 95% confidence interval [CI]: 0.33–0.54; burned NS = 0.24, 95% CI: 0.10–0.46). The amount of bare ground was negatively associated with NS, but effects diminished as the amount of bare ground reached low levels. Shrub height and visual obstruction were positively associated with NS during the entire study period, whereas minimum Tbb had a weaker effect. Our findings demonstrate that thermoregulatory selection by Greater Sage-Grouse at nest sites had marginal effects on their NS. However, given that increases in vegetation structure (e.g., shrub height) provide thermal refuge and increase NS, vegetation remnants or regeneration in a post-fire landscape could be critical to Greater Sage-Grouse nesting ecology.

Temporal mismatch in space use by a sagebrush obligate species after large‐scale wildfire

“…Thus, the temporal lag we observed likely reflects the point at which the shrub canopy had returned to levels that fulfilled sage‐grouse life history needs for summer (<16.9%; Hagen et al, 2007) and winter (10%–30%; Hupp & Braun, 1989). Our findings support previous reports of the damaging effects of the loss of sagebrush on sage‐grouse space‐use and potentially population dynamics (Anthony et al, 2021; Dahlgren et al, 2010; Green et al, 2017; Smith & Beck, 2018; Walker et al, 2007, 2020).…”

“…The distribution of sage‐grouse has contracted by ~50%, with concurrent species‐level population declines, coinciding with the loss and degradation of sagebrush ecosystems (Knick & Connelly, 2011), which has made them the focal species of conservation and research of the sagebrush biome in recent years. Studies have reported negative effects of wildfire on the structure, function, or composition of sage‐grouse habitat and population demographics or growth (Anthony et al, 2020, 2021; Blomberg et al, 2012; Coates, Casazza, et al, 2016; Davis & Crawford, 2015; Foster et al, 2019; Nelle et al, 2000). Yet, few studies have examined how wildfire influences sage‐grouse habitat selection and space use (Byrne, 2002; Foster, 2016; Lockyer et al, 2015).…”

“…In August 2012, the Holloway megafire burned 186,499 ha resulting in a mosaic of burn severity patches throughout the Trout Creek Mountains in Oregon and Nevada. Research began in 2013 to evaluate how a population of sage‐grouse responded to post‐wildfire sagebrush communities (Anthony et al, 2021; Foster et al, 2019). As of 2019, the Trout Creek Mountains supported the second largest known number of lek complexes in Oregon, making this population of sage‐grouse of particular interest to monitor following a disturbance (Oregon Department of Fish and Wildlife, 2019).…”

Greater sage‐grouse respond positively to intensive post‐fire restoration treatments

“…Although sage‐grouse response to fire has been investigated previously (e.g., Anthony et al, 2021 ; Lockyer et al, 2015 ), little information is available about how post‐fire restoration treatments affect patterns in resource selection by sage‐grouse. To address this information gap, we used telemetry data to evaluate habitat selection by sage‐grouse in each of 3 years after a large wildfire in sagebrush steppe in the Intermountain West.…”

Acute and lagged fitness consequences for a sagebrush obligate in a post mega‐wildfire landscape

“…The lack of sagebrush cover ( = 2%) and high cheatgrass cover ( = 12%) provided low quality nesting habitat within burned Wyoming big sagebrush communities in our study area (Anthony et al, 2020). Despite these unfavorable nesting conditions, sage‐grouse selected fine‐scale vegetation features within burned areas, which provided thermal and concealment cover, a strategy which increased NS (Anthony et al, 2021).…”